Model airplane or glider



W. E. BACK May 9, 1939.

MODEL AIRPLANE OR GLIDER Filed Oct. 15, 1937 2 Sheets-Sheet 1 May 9,1939. w. E. BACK MODEL AIRPLANE OR GLIDER Fi led Oct. 15, 1957 2Sheets-Sheet 2 WA-TEA r, 7

Patented May 9, 1939 UNITED STATES PATENT OFFIQE Application October 15,1937, Serial No. 169,293 In Great Britain October 23, 1936 9 Claims.

This invention relates to model airplanes or gliders (hereinafterreferred to as gliders) and means for launching such gliders, and hasfor its main objects to provide an improved glider 5 which will performsatisfactorily both during launching and during flight, Will not bereadily damaged if it strikes obstructions and will generally fulfil therequirements of toys of this kind.

To this end a model glider according to the m present inventioncomprises a longitudinal spar or framework constituting the body of theglider and adapted to carry main and tail planes, a main plane, andresilient means for connecting the main plane to the spar in such amanner that on the occurrence of a lifting force on the plane,sufficient to cause movement of the plane against the action of theresilient means, the angle of incidence of the plane will be reduced.Thus the resilient means are conveniently such that on the occurrence ofa lifting force substantially in excess of that exerted thereon duringnormal flight, the plane will move against the action of the resilientmeans in the manner referred to. It will be understood of course thatthe main plane is arranged so that although it can move in the mannermentioned under the action of a sufficient lifting force it is normallyheld from other movement relative to the body.

When a model glider is being launched, for

.".'. example by means of a stretched elastic or other catapult device,the speed is generally greatly in excess of the normal flying speed withthe result that the glider immediately on release from the catapulttends to perform a loop of limited mean radius which may bring it intoviolent contact with the ground in spite of the fact that the upwardpart of such a loop is generally of large mean radius as compared withthe downward part. With the present invention, however, when during andimmediately after the launching operation the glider has a speedsubstantially in excess of the normal flying speed, the upward pressureon the main plane causes movement of this plane to reduce the angle ofincidence with the result that the glider, on

release from the catapult, tends either to perform a loop of large meanradius carrying it a considerable height above the ground before thedescending part of the loop occurs, or to rise 50 into the air Withoutperforming a loop. As the speed of the glider falls following launching,the upward pressure on the main plane also falls so that by the time thespeed of the glider has fallen to its normal flying speed, the resilient55 means will have rettuned the main plane to its normal flying positionin which the glider will fly or glide satisfactorily at such normalflying speed. It will further be appreciated that by varying theeffective force of the resilient means, the performance of the glider onrelease from the catapult can be varied.

Preferably the main plane is connected to the spar by resilient meansdisposed at a point in advance of the centre of pressure of the plane sothat not only is the angle of incidence of the plane reduced on theoccurrence of a lifting force sufficient to cause movement of the planeagainst the action of the resilient means but the resilient means alsopermits other movements of the plane if the plane or the body meets anobstruction during flight. In this way the tendency for the glider to bedamaged due to meeting such an obstruction is reduced. Thus, the mainplane is conveniently connected to the body at a point in advance of thecentre of pressure of the plane by one or more resilient bands passinground a part of the plane and anchored to pins or other securing meanswithin the body below the plane. Such resilient band or bands may passthrough two holes or slots in the main plane or around the leading edgeof the plane and through a hole or slot in the main plane, the movementof the main plane to reduce the angle of incidence taking place aboutits leading edge or a point adjacent thereto.

The term band is to be understood as including a length of resilientmaterial not necessarily of an endless character and of any suitablecrosssection.

When the main plane is connected to the body at a point in advance ofthe centre of pressure of the plane, in the manner indicated above,independent auxiliary means may also be provided for resisting upwardmovement of the trailing edge of the plane relatively to the body beyonda predetermined point, such means preferably being resilient andcomprising, for example, a rubber band extending between the trailingedge of the plane and a pin or other anchorage on the body. In such anarrangement this rubber band is preferably slack when the plane is inits normal flying position so that it does not come into effectiveoperation until a predetermined upward movement of the trailing edge ofthe plane has occurred. In an alternative arrangement, the auxiliarymeans for resisting upward movement of the trailing edge of the planemay include a lost motion device of the pin and slot type permittinglimited upward movement of the trailing edge before the auxiliaryresilient means resisting such upward movement come into operation. Inany case, not only the main means for resiliently connecting the mainplane to the body but also the auxiliary means for resisting upwardmovement of the trailing edge of the plane may be arranged so that theforce exerted thereby on the plane can be varied or the point in theupward movement of the trailing edge of the plane at which the auxiliarymeans come into operation can be altered.

The main plane which is preferably formed of thin plywood isconveniently provided with a reinforcing lath extending along the wholeof the under surface of its leading edge, this lath being suitablyshaped and conveniently gumrned or otherwise secured to the plane whileits centre part rests on an appropriately shaped seating on the uppersurface of the body. In such a construction, when one or more rubberbands constitute the main resilient means for connecting the main planeto the body, these bands conveniently pass round the leading edge of theplane and through a slot in the plane immediately behind the lath.

The under surface of the body is preferably substantially straight whilethe upper surface is curved so that the forward end of the body is deepcompared with the after end and in a convenient arrangement the bodycomprises two identical side members formed of sheet material andconnected together in spaced relationship by distance pieces to whichthe side members are secured, as by adhesive. In such a construction therubber bands or like resilient means for securing the plane to the bodyconveniently extend between the side members.

A vertical fin is preferably provided at the after end of the body, thisfin lying above a tail plane which is pivotally secured to the lowersurface of the body so that it can move about a vertical axis to allowswivelli-ng of this tail plane if one end thereof hits an obstruction.

The catapult device for launching the glider may be of the kindcomprising a mast, say 6 or '7 feet high, provided with stays forsupporting it substantially vertically on the ground and adapted to haveconnected to its upper end one end of a length of elastic the other endof which is adapted to engage a hook at the forward end of the glider.The means for connecting one end of the elastic to the uper end of themast are, however, preferably such that if, during stretching of theelastic, the mast should be pulled over, the end of the elastic willslip from the securing means at the top of the mast. In this way, riskof the mast being pulled by the stretched elastic at high speed towardsa person stretching the elastic preparatory to launching the glidershould the mast be pulled over by the force of the elastic, is avoided.

The invention may be carried into practice in various ways but oneconstruction according to the invention is illustrated by way of examplein the accompanying drawings, in which- Figure 1 is a perspective viewof the complete glider,

Figure 2 is a sectional side elevation on an enlarged scale of theforward part of the glider,

Figure 3 is a section on the line $-3 of Figure 2,

Figure 4 is a plan view of the forward part of the glider with the endsof the main plane omitted for convenience,

Figure 5 is a cross-section of the main plane on the line 55 of Figure1, and

Figure 6 shows a modification.

In the construction illustrated, the glider comprises a spar orframework constituting the body of the glider and formed from two sidemembers A, A connected together and spaced apart by intermediatedistance pieces B, B B B connected, for example by gluing, to the sidemem bars which are cut away as shown for lightness. Secured to the afterend of the body is a vertical fin C formed, for example, of thin plywoodwhile a tail plane D, which may also be formed of thin plywood and isconveniently reinforced at D is pivotally connected, for example by ascrew D to the under surface of the body. Secured, as by gluing, to thetwo side members, as shown, are two cheeks E the upper surfaces of whichare shaped to receive the shaped under surface of a lath F extendingalong and secured as by gluing throughout its length to the undersurface of the leading edge of the main plane F which is convenientlyalso formed of thin plywood. When the main plane is thus formed of thinplywood, the grain of the two sheets constituting the outer pliespreferably runs from the leading to the trailing edge. This tends togive greater strength to the plane, enables the plane to be cambered bypressing and also provides flexibility allowing the trailing edge tomove upwards under air pressure thus increasing the stability of theairplane or glider and at the same time assisting one of the purposes ofthe flexible attachment of the plane to the spar in the mannerdescribed.

In some cases additional strength may be given to the part of the mainplane immediately behind the lath either by securing to the upper orlower surface of this part of the plane an additional sheet of material,for example thin plywood, or by providing short ribs on the upper orunder surface of this part of the plane, the ribs or other reinforcementextending from the lath towards the trailing edge but terminating shortof the trailing edge so as to leave a flexible portion of the planeadjacent to the trailing edge. In the case of ribs, these would probablybe attached to the lath at suitable intervals along the wing span while,in the case of a reinforcement of sheet material, this would preferablyextend forwards to a point beyond the after edge of the lath.

Formed in the centre of the plane F behind the lath F is a slot Fthrough which is adapted to pass a rubber band G passing also round thefront of the main plane and engaging at its lower ends pins G G passingthrough holes in the side members so as to connect the plane resilientlyto the body in such a manner that the aggregate elastic pull is at apoint in front of the centre of pressure of the plane. It will be seenthat the rubber band G passes downwards through a gap between the afterend of the distance piece B and the forward end of the distance piece Bthis gap being sufiicient to permit a degree of forward and backwardmovement of the plane without the band coming into engagement with thesedistance pieces and the edges of the distance pieces being rounded offto prevent damaging the rubber. Conveniently a strip of flexiblematerial, for example rubber, extends from the distance piece B toapproximately the leading edge of the plane, as shown at B to provide astreamline effect, this strip either being thickened or carrying amember B at its after end the upper surface of which runs more or lesssmoothly into the upper surface of the plane and band G. Pins G Gconveniently extend across the space between the side members at pointsa short distance in advance of the two downwardly extending parts of therubber band G so as to engage this rubber band on forward movement ofthe plane, for example if the body of the glider meets an obstructionand the plane is thus jolted forward. In this way the forward or othermovement of the plane is permitted but is resiliently resisted in amanner tending to prevent damage of the plane when landing or if anobstruction is struck during flight. It will be understood that theshaping of the upper surfaces of the two cheeks E in relation to theshape of the lath F is such as to maintain the plane normally at rightangles to the body while permitting movement of the plane relatively tothe body for the purpose referred to.

Secured, as by adhesive, in a part-cylindrical groove extending alongthe whole of the forward end of the lath F is a length of rubber H ofcircular cross-section and either tubular or not, adapted to act as abuffer to prevent damage should the forward edge of the plane hit anobstruction, reinforcing strips H of gummed tape or the like passinground the end portions of this rubber buffer. A strip of gummed tape orthe like H also conveniently passes round the centre part of the leadingedge of the main plane and extends over the adjacent upper and lowersurfaces of the plane adjacent to the rubber band G, as shown.

Secured to the centre of the length of the trailing edge of the plane,for example by adhesive tape J, is a length of wire J the adhesive tapeand a section of the trailing edge of the plane being cut away, as shownat J so as to expose the centre part of the wire which thus forms a pinround which passes a rubber band K the lower portion of which passesround a pin K extending between the side plates, as shown. Alternativelythe band K may pass wholly through the slot and be anchored by aseparate pin. The arrangement is preferably such that when the planeoccupies its normal flight position, as shown, this rubber band is onlyslightly in tension.

Secured to the forward end of the body is a tubular rubber buffer Lwhich may carry the hook L adapted to engage the elastic of thelaunching catapult and is held in place by a metal plate L forming anupward extension from the forward end of a metal member L of channelsection secured to the under surface of the forward end of the body andacting as a weight to counterbalance the after portion of the glider.

Instead of the rubber band K directly engaging a pin secured to thetrailing edge of the plane, the upper end of this rubber band may havesecured to it a slotted link M, as shown in Figure 5, constituting theslotted part of pin and slot mechanism of which the pin is constitutedby the pin J In this construction the rubber band would conveniently bearranged with more tension and the link M would be arranged so that ithas a part which normally rests on the upper surface of the body, asshown.

Again, if desired, instead of the rubber band K engaging a pinconstituted by a length of wire secured to the trailing edge of theplane F as shown, a slot may be provided in the plane adjacent to itstrailing edge with a pin extending across this slot to receive therubber band, in which case the part of the plane surrounding the slot ispreferably reinforced by securing to its two faces, as by glue, sheetsof thin plywood or other sheet material.

In any case, it will be seen that the rubber band K not only tends tolimit the upwardmovement of the trailing edge of the plane above apredetermined point but resists while permitting swivelling of the planeabout a vertical axis, for example if the plane hits an obstruction whenin flight, thus tending to prevent either end of the plane hitting theVertical fin C.

In an alternative arrangement, instead of or in addition to providingthe rubber band K, the slot F may be arranged nearer the trailing edgethan indicated so as to increase the resistance exerted by the rubberband G to swivelling movement of the main plane about a vertical axis.

In a still further alternative arrangement, a light metal or likefitting may be secured to the upper surface of the main plane above thelath F to carry pins round which rubber bands pass, each rubber bandpassing from its pin either through a slot in the plane or round theleading edge of the plane and being anchored as by a fin'ther pin withinthe spar. In such an arrangement the pins in metal fitting may be thusnormally removed to release the rubber bands when the plane is to bedetached from the spar.

Although in the construction illustrated the plane comprises a sheet ofthin material to the under surface of the leading edge of which issecured a reinforcing lath, other constructions may, of course, beemployed. For example, the plane may be made from one piece of woodsuitably hollowed out and shaped by appropriate machinery and taperingfrom a relatively thick portion adjacent the leading edge to thetrailing edge which may be as thin as is practicable. Where the planecomprises thin sheet material such as thin plywood and a reinforcinglath, as shown in the drawings, however, it is possible to camber theplane by a suitable pressing operation and this method is generallypreferred.

The drawings illustrate the glider in skeleton form. In practice,however, the side members and upper and under surfaces of the body maybe covered with suitable fabric or other sheet material so as to reducewind resistance due to air eddies. In this case suitable slots, whichcould be provided with removable cover plates, would be provided toenable the rubber bands to be threaded and, where necessary, stretchedinto position and the necessary pin or pins inserted to secure them inplace.

It will be understood that the main plane can readily be removed fromthe body by removing one of the pins G G2 and the pin K In order tofacilitate the threading and positioning of the rubber band G when theplane is to be replaced, one end of this rubber band is convenientlyattached to a short length of tape or the like, as shown at G by whichthe rubber band can be held in its stretched position while theappropriate pin G is inserted through its looped end.

In a modification two or more rubber bands may be employed, each bandbeing anchored to the spar for example in the same way as the band G,the bands being either superimposed or arranged side by side. Again, twoor more alternative holes may be provided to receive the pin G or thepin K or both to permit adjustment of one or both rubber bands.

It will be seen that the mode of attachment of the main plane not onlyenables the trailing edge to move upwards so as to reduce the angle ofincidence when the lifting force exerted on the plane is raised abovethe normal during the launching operation but also permits the mainplane to move against the action of the rubber bands if the body or theplane hits an obstruction thus reducing risk of damage to the plane.Moreover, the formation of the body with a deep forward end tends toprotect the vertical pin C from striking an obstruction when the glideris in flight while the pivotal connection for the tail plane D enablesthis to swivel should one end of it hit an obstruction.

It will also be seen that by disconnecting the rubber bands G and K themain plane can readily be detached from the spar to facilitate packingand transport.

It is to be understood that the constructions more particularlydescribed above are given by way of example only and that theseconstructions may be modified within wide limits without departing fromthis invention.

What I claim as my invention and desire to secure by Letters Patent is:

l. A toy glider including in combination a longitudinal framework, alongitudinal seating formed on the framework and having a substantialarea, a main lifting plane part of which adjacent its leading edge restson said seating which is formed to maintain the plane .at the correctangle of incidence for normal flight, at least rubber band acting on themain plane in advance of the center of pressure of the plane to hold theplane normally on the seating but to permit the plane to move about avertical axis should one end strike an obstruction and to move about apart adjacent its leading edge to reduce the ngle of incidence of theplane on the occurrence of a lifting force thereon substantially inexcess of that exerted during normal flight, and means for anchoringeach rubber band to the framework.

2. A toy glider including in combination a longitudinal framework, alongitudinal seating formed on the framework and having a substantialarea, a main lifting plane part of which adjacent its leading edge restson said seating which is formed to maintain the plane at the correctangle of incidence for normal flight, at least one slot formed in themain plane adjacent the center of its length and in advance of thecenter of pressure of the plane, at least one rubber band passing roundthe leading edge of the plane and through the slot therein, and meansfor anchoring the rubber band to the framework so as to maintain theplane normally on its seating but to permit it to move about a verticalaxis should one end strike an obstruction and to move about a partadjacent its leading edge to reduce the angle of incidence of the planeon the occurrence of a lifting force thereon substantially in excess ofthat exerted during normal flight.

3. A toy glider including in combination a longitudinal framework, alongitudinal seating formed on the framework and having a substantialarea, a main lifting plane part of which adjacent its leading edge restson said seating which is formed to maintain the plane at the correctangle of incidence for normal flight, at least one rubber band acting onthe'main plane in advance of the center of pressure of the plane to holdthe plane normally on the seating but to permit the plane to move abouta vertical axis should one end strike an obstruction and to move about apart adjacent its leading edge, and resilient means acting on thetrailing edge of the plane for limiting upward movement thereof androtational movement of the plane about a vertical axis.

4. A toy glider including in combination a longitudinal framework, alongitudinal seating formed on the framework and having a substantialarea, a main lifting plane comprising a strip of sheet material to thelower face of the leading edge of which is secured, as by adhesive, areinforcing lath extending substantially throughout the length of theleading edge of the plane and part of which rests on said seating whichis formed to receive the lower face of the lath and thus maintain theplane at the correct angle of incidence for normal flight, at least oneslot formed in the main plane adjacent the center of its length and inadvance of the center of pressure of the plane, at least one rubber bandpassing round the leading edge of the plane and through the slottherein, and means for anchoring the rubber band to the framework so asto maintain the lath on the seating, but to permit the plane to moveabout a vertical axis should one end strike an obstruction and to moveto re duce the angle of incidence of the plane on the occurrence of alifting force thereon substantially in excess of that exerted duringnormal flight.

5. A toy glider including in combination a longitudinal framework, alongitudinal seating formed on the framework and having a substantialarea, a main lifting plane comprising a strip of sheet material alongthe lower face of the leading edge of which is attached, as by adhesive,a reinforcing lath part of which rests on the seating which is formed toreceive the lower face of the lath and thus maintain the plane at thecorrect angle of incidence for normal flight, a slot formed in the planeadjacent the center 01" its length and immediately behind thereinforcing lath, at least one rubber band passing round the leadingedge of the plane and through the slot, and means for anchoring therubber band to the framework below the plane so as to maintain the lathon the seating but to permit it to move about a vertical axis should oneend strike an obstruction and to move to reduce the angle of incidenceof the plane on the occurrence of a listing force thereon substantiallyin excess of that exerted during normal flight.

6. A toy glider including in combination a longitudinal frameworkadapted to carry a main lifting plane and a tail plane, the frameworkcomprising two identical side members formed of sheet material connectedto one another and spaced by distance pieces to which the side mem bersare secured, as by adhesive, with gaps between the distance pieces, alongitudinal seating formed on the framework and having a substantialarea, a main plane comprising a strip of sheet material to the lowerface of the leading edge of which is secured, as by adhesive, areinforcing lath extending substantially throughout the length of theleading edge of the plane and part of which rests on said seating whichis formed to receive the lower face of the lath and thus maintain theplane at the correct angle of incidence for normal flight, at least oneslot formed in the main plane adjacent the center of its length and inadvance of the center of pressure of the plane, at least one rubber bandpassing round the leading edge of the plane and through the slot thereinand between two of the distance pieces and means for anchoring therubber band within the framework so as to maintain the plane on itsseating but to permit it to move above a vertical axis should one endstrike an obstruction and to move about a part adjacent its leading edgeto reduce the angle of incidence of the plane on the occurrence of alifting force thereon substantially in excess of that exerted duringnormal flight.

7. A toy glider including in combination a longitudinal framework, alongitudinal seating formed on the framework and having a substantialarea, a main lifting plane part of which adjacent its leading edgesrests on said seating which is formed to maintain the plane at thecorrect angle of incidence for normal flight, at least one slot formedin the main plane adjacent the center of its length and spaced from theleading edge, at least one resilient rubber band passing round theleading edge of the plane and through the slot, means for anchoring therubber band to the framework below the plane, and stops disposed a shortdistance in front of at least one part of the rubber band which extendsfrom the main plane to the anchoring means to impose an increasedresistance to forward movement of the plane beyond a predeterminedpoint.

8. A toy glider including in combination a longitudinal frameworkadapted to carry a main lifting plane and a tail plane, the frameworkcomprising two identical side members formed of sheet material connectedto one another and spaced by distance pieces to which the side membersare secured as by adhesive with gaps between the distance pieces one gapconstituting a slot in the upper face of the framework, a longitudinalseating formed on the framework and having a substantial area, a mainplane comprising a strip of sheet material along the lower face of theleading edge of which is attached, as by adhesive, a reinforcing lathpart of which rests on the seating which is formed to receive the lowersurface of the lath and thus maintain the plane at the correct angle ofincidence for normal flight, a slot formed in the plane adjacent thecenter of its length and immediately behind the reinforcing lath, atleast one rubber band passing round the leading edge of the plane andthrough the slot therein and through the said slot in the upper face ofthe framework which is of sufficient dimensions to permit limited foreand aft movement of the main plane, in addition to swinging movementabout a vertical axis should one end of the plane meet an obstructionand means for anchoring each rubber band to the framework.

9. A toy glider having a longitudinal frame-

